Traditionally, computer display screens have been designed either to provide a "portrait" orientation, in which the vertical dimension is greater than the horizontal dimension, or to provide a "landscape" orientation, in which the horizontal dimension is greater than the vertical dimension. Recent advances in technology have made possible the use of both portrait and landscape orientations with the same computer. Some computer display systems allow the user of the computer to reposition a display screen between portrait and landscape orientations, and some computers allow the simultaneous use of multiple display screens. When the orientation of a display screen is repositioned between portrait and landscape orientations, some display area is necessarily lost from view and other area is gained. In a computer system that uses "window" based displays, the area that is lost may include important portions of a window necessary to allow the user to move or resize the window. There may also be other screens displaying data which do not change in orientation. In order to ensure that the resulting display is usable, some method for automatically redefining the coordinate system of the computer displays in the system, and resizing and moving windows, is desirable.